Template Synthesis of Co(II), Ni(II) and Cu(II) Complexes Derived From Oxamide Ligand and the Reactivity of Cu(II) Complex Towards Human Serum Albumin

A new oxamide ligand 2,2'-(oxalydimino)bis(diacetic acid)[C(10)H(11)O(10)N(2)],[L] has been synthesized by the condensation reaction of Iminodiacetic acid and Diethyloxalate. This ligand [L] was further allowed to interact with triethylene-tetraamine metal complexes [C(16)H(26)N(6)O(8)M]Cl(2) (where M=Co(11), Ni(11) and Cu(11)) to yield the new N4 macrocyclic complexes 3, 3', 6, 6' tetraazadodeca 1-1' diimino N N tetraacetic acid M) chloride ([C(16)H(26)N(6)O(8)Co]Cl(2), [C(16)H(26)N(6)O(8)Ni]Cl(2) and [C(16)H(26)N(6)O(8)Cu]Cl(2)). These complexes were characterized by elemental analyses, i.r., n.m.r., e.p.r, and u.v.-vis spectroscopy. All the complexes show square planar geometry and are ionic in nature. The kinetic studies of the Cu(lI) complex were ascertained spectrophotometrically by observing the absorbance changes in presence of protein Human Serum Albumin (HSA) in phosphate buffer at different pH's at 30(0)C. The absorbance changes were monitored at 278 nm (λ(max) of HSA) with respect to time and pseudo-first-order rate constants, kobs, were obtained from the slope of the straight line using the least squares regression method. The electrochemical behaviour of the Cu(ll) complex was monitored by cyclic voltammetry in a phosphate buffer. The E(p) values-0.730 and-0.560 V respectively, were obtained at the scan rate of 0.1 Vs(-1). The interaction of the Cu(II) complex with the HSA was studied at the same scan rate, which reveals weak binding as the E(0) values do not shift considerably. The cyclic voltammogram of the Cu(II) complex bound to HSA was recorded at different pH's also (6.5 to 7.4). The pH-rate profile data reveals that the reactions are pH dependent.